The interfacial reactions between In49Sn solders and Ag thick films at temperatures ranging from 200°C to 350°C have been studied. The intermetallic compound formed at the Ag/In49Sn interface is Ag 2 In enveloped in a thin layer of AgIn 2 . Through the measurement of the thickness decrease of Ag thick films, it has been determined that the reaction kinetics of Ag 2 In has a linear relation to reaction time. Morphology observations indicated that the linear reaction of Ag 2 In was caused by the floating of Ag 2 In into the In49Sn solder as a result of the In49Sn solder penetrating into the porous Ag thick film. A sound joint can be obtained when a sufficient thickness of the Ag thick film (over 19.5 m) reacts with the In49Sn solder. In this case, the tensile tested specimens fracture in the In49Sn matrix.

Intermetallic compounds formed during the soldering reactions between Sn-3.5Ag and Cu at temperatures ranging from 250°C to 375°C are investigated.The results indicate that scallop-shaped η-Cu 6 (Sn 0.933 Ag 0.007 ) 5 intermetallics grow from the Sn-3.5Ag/Cu interface toward the solder matrix accompanied by Cu dissolution. Following prolonged or higher temperature reactions, ε-Cu 3 (Sn 0.996 Ag 0.004 ) intermetallic layers appear behind the Cu 6 (Sn 0.933 Ag 0.007 ) 5 scallops. The growth of these interfacial intermetallics is governed by a kinetic relation: ∆X ϭ t n , where the n values for η and ε intermetallics are 0.75 and 0.96, respectively. The mechanisms for such nonparabolic growth of interfacial intermetallics during the liquid/solid reactions between Sn-3.5Ag solders and Cu substrates are probed.

No abstract

No abstract

No abstract